Electron multiplier



J1me 0- H. w- LANGENwALTER ELECTRON MULTIPLIER Filed Feb. 22, 1958 Patented June 11, 1940 ELECTRON Hans Wolfgang Langenwal Germany, assignor to rn'rsur MULTIPLIER ter, Berlin-Zehlendorf, the firm of Fernseh Aktiengesellschaft, Zehlendorf, Germany Application February 22, 1938, Serial No. 191,851 In Germany February 20, 1937 4 Claims.

Electron multipliers are known in which the primary current is multiplied by means of several electron-permeable secondary emitting electrodes arranged in consecutive order. These secondary 5 emitting electrodes may have the form of meshworkasieves or foils.

In such arrangements the danger often arises that lateral electrical fields deflect the electrons from the desired paths, and thereby withdraw them from further multiplication. This may be the case particularly if electrodes are disposed in the proximity of the multiplying arrangement, which electrodes have a positive potential in respect to at least several of the secondary emitting electrodes. For instance, in Farnsworth dissector tubes, it is preferable for circuit reasons to dispose the secondary emitting electrodes inside of a screening cylinder, the potential of which is positive in respect to all or at least to several secondary emitting electrodes.

In order to avoid or decrease the influence of lateral accelerating fields, it is the object of the invention to provide several or all secondary emitting electrodes with a curvature in the direction towards the primary source of electrons in the multiplying arrangement. An accelerating field is then formed between two secondary emitting electrodes, which field possesses a lateral component in the direction toward the axis of the system and thereby exerts a concentrating efiect upon the electron stream. Simultaneously, the shape of the secondary emitting electrodes has a certain screening eifect upon the interior of the multiplier.

Thedrawing shows an emb vention. The entire arran in a vacuum receptacle ll, representative of a Farnsworth dissector tube. The cylindrical screen i, provided with a minute aperture i 2, 40 surrounds an oblique plate l3 having a second. arily emissive surface, the secondary emitting grids 2 to 8, an electron-permeable anode 9 and a solid secondarylemitting electrode I 0. Electrons emitted from the photoelectric cathode (not shown) of the Farnsworth dissector tube enter the screen I through the aperture I 2 and ocliment of the ingement is disposed impact the plate l3, whereby they produce secondary electrons. For the explanation of the invention, the plate I3 will be considered as the source of primary electrons for the remainder of the multiplier structure inasmuch as the type of source of the primary electrons is immaterial to the invention. The majority of the electrons travels through the anode 9 after multiplication at the grids 2 to 8, impacts the plate I0 and efiects.

at a potential positive in res emitting electrodes.

nected with a screen which leads to the in fier.

on th put of this plate. In this obtained than would re used as collecting nder I may be held pect to all secondary It may be conductively cone outside of the tube the following ampli- The curvature of the secondary emitting electrodes is, as may be seen from the drawing, adjusted in accordance with the potential difierence between the respective secondary emitting electrodes and the surrounding cylinder, i. e.

the curvature is increase d with increasing potential difference. Plate ID has a concave cur ture in respect to the anode because a reversal of the electron paths take While, in this case, the

surrounds the secondaryemit these are given spherical cur tion can obviously also be a the electrodes, whose fields plier arrangement, are, for i on two opposite sides of the ment. In such a case, it the secondary emitting ele tion only, i. e., cylindrically It may be understood th s place at this plate.

cylinder completely ting electrodes, and vatures, the inven pplied in cases where reach into the multi-. nstance, located only multiplying arrangemay suiiice to curve ctrodes in one direcat the invention can also be applied to multipliers which possess one or several solid secondar front or in back of a seri electrodes.

I claim:

1. An electron multiplier source of electrons, a plurality of ondary emissive electrodes, positioned between two of sive electrodes, said seconda being of concave shape as viewe lector electrode, the decrease,

y emitting electrodes in es of electron-permeable e comprising a successive secector electrode econdary emisissive electrodes d from said colin the radii of devic a coil said s ry em curvature of said electrodes progressing more rapidly than the increase secondarily emissive electr lector.

2. An electron multiplier source of elect last of said electrodes on th collector electrode being 00 said source of electrons.

in spacing of said odes from said (:01-

device comprising a rons, a plurality of successive secondary emissive electrodes, a collector elece last and the precedy emissive electrodes, those of ectrodes on one side ein g of concave shape f electrons and the e other side of said nvex as viewed from 3. An electron multiplier device having a source of electrons, a collector electrode and a plurality of secondary emissive electrodes intermediate said source of electrons and said collector electrode, said secondary emissive electrodes being of convex shape as viewed from said source of electrons with the convexity of each succeeding electrode varying. with respect to the preceding electrode.

4. An electron multiplier device comprising a secondary emissive electrodes, a collector electrode positioned between two of said secondary emissive electrodes, those of said secondary emissive electrodes on one side of said collector electrode being of concave shape as viewed from said collector electrode, with the radius of curvature of said secondary emissive electrodes decreasing with increasing distance from said collector electrode.

HANS WOLFGANG LANGENWALTER.

source of electrons, a plurality of successive 

